The Slim Line I Low Profile Clamping System makes clamping difficult items fast and easy for smaller designs such as pockets of tote bags, computer cases, and backpacks. There are nine windows available separately and include the following sizes: 2.5"x4", 3.5"x5.5", 4.5"x4.5", 5.5" round, 5.5"x3.5", 2.5 round, Left and Right side of cap and 6.5" x 5". Choose the window options that best fit your work and add additional windows when needed. To attach clamp, remove your arms from your machine and use the screws from the arms and attach the clamp to the back bar of your machine. You hoop on your machine.